Predator functional response is a key element of feeding interactions that quantify the per capita feeding rates of predators depending on prey density, and variation in its parameters is strongly associated with interaction strength and population dynamics. We studied 18 functional responses of the marine whelk-bivalve systems across three levels of predator body size and three prey species at two habitat structures. We found that the marine whelk can be a handling-limited predator which received less attention so far. We propose that the handling-limited predator can further be categorized into two types: pursuing-limited (where maximum feeding rate could be influenced by habitat complexity) and ingesting-limited (where maximum feeding rate is impacted not by habitat complexity, but predator-prey body mass ratios and prey defense strategy). Our results show that handling time scales negatively with predator-prey body mass ratios, but there are layers of complexity nested within this trend. We first provide an underlying mechanism of this trend is the transition from handling to digestion limitation with increasing predator-prey body mass ratios. In addition to confirming known body mass ratios and habitat structure effects, our study confirms the importance of prey types. Our study reveals that simple assumptions about body masses and prey defense strategy may usefully refine estimates of feeding interactions in complex food webs.